This application claims the priority of German application 197 35 834.9-21, filed in Germany on Aug. 18, 1997, the disclosure of which is expressly incorporated by reference herein.
The invention relates to an operating element in a motor vehicle having a hollow gripping section which can be gripped by an occupant, which is arranged above a leg space of the motor vehicle and is provided with air outlet openings in a ventilatable manner, to which air outlet openings air is guided through an air guiding duct which flows out into an occupant compartment through the air outlet openings.
From German Patent Document DE 21 64 976 A1, an operating element is known in the form of a steering wheel for a motor vehicle, whose gripping section on the steering wheel rim is supplied by way of connecting and feeding tubes, which are connected with the warm air and cooling air sources existing in the vehicle, with warm and cold air which can emerge by way of the steering wheel spokes and the steering wheel rim. In this case, for cooling or warming the driver's hands, corresponding air is actively supplied to the steering wheel rim.
In German Patent Document DE 37 13 450 A1, an arrangement is described for tempering steering and switching devices where the heating and cooling energy is supplied in the form of gas, liquid and/or electric energy, for which feeding and removal lines to a steering column are provided in a closed circuit or for an external energy supply.
Also according to an embodiment of a steering wheel in German Patent Document DE 23 22 484 A1, an active air feeding is provided to a steering wheel hub by means of which the fresh air or the heating air is blown against the driver from the baffle plate.
In U.S. Pat. No. 4,640,340 A1, a steering wheel with a heat exchanger is described from which a heated or cooled liquid can be transported into the central tube of the steering wheel rim.
In the embodiment of a steering wheel described in French Patent Document FR 26 82 071 A1, the Peltier effect is used for the cooling or the heating of a steering wheel.
Concerning the general background of the external ventilating of steering wheels, reference is also made to U.S. Pat. No. 4,562,957 A1 and U.S. Pat. No. 4,679,730.
An object of the invention consists of reducing the energy consumption for ventilating the gripping section of an operating element of a motor vehicle.
This object is achieved according to preferred embodiments of the invention by providing an arrangement wherein the air guiding duct starts in a leg space of the occupant compartment, and wherein, from a gripping section heated by the effect of the sun, warmer air can flow off through the air outlet openings into the occupant compartment, and, in the process, by way of the air guiding duct, cooler air is taken from the leg space into the gripping section.
Under the effect of the sun, operating elements in a motor vehicle may heat up considerably so that they can hardly be touched in their gripping section without pain.
In sun-irradiated vehicles, the sun radiation in the occupant compartment results in a temperature increase of approximately +20.degree. C. starting from the leg space (30.degree. C.) to the level of the steering wheel.
Because of the operating element which, as the result of the radiation of the sun is often heated by another 30.degree. C. and more, by means of the air guiding according to the invention, the air can emerge from the operating element because of its lower density through the outlet openings into the occupant compartment and in the process--because of the resulting vacuum--sucks up the cooler air through the air guiding duct from the leg space of the occupant compartment. The gripping section of the operating element is cooled because of this passive ventilation.
Particularly for the gripping section of a steering wheel on the steering wheel rim, this passive ventilation has a very positive effect because the uniform tempering of the steering wheel rim surface ensures a secure and pleasant grip around the steering wheel rim in the driving operation.
This effect is particularly noticeable when the vehicle is parked and heated by the sun, where, in a passive manner, relatively cool air is pulled from the floor area into the steering wheel without requiring electric current or a running fan for this purpose. By means of a thermal insulation of the air guiding duct, the cool air from the leg space does not unnecessarily heat up on its way.
Also when a fan is used for the air transport, advantages are achieved in connection with the passive ventilating because the energy required for the fan will be lower.
In certain preferred embodiments, spaced knit under the air-permeable cover of the operating element also has an air-permeable construction and separates the cover with the contact surface thermally from the metallic, considerably heating-up, interior frame of the operating element. Because of the spaced knit, the cover stores little heat or coldness and is adapted more rapidly to the palm temperature of the gripping person.
In certain preferred embodiments, because of the construction of an intermediate layer as a knit, for example, woven from threads, the cover receives from it a high uniform air supply as the result of which the flow-out on the cover is hardly noticeable. In addition, a soft, elastic gripping sensation can be achieved.
For heating up the gripping section of the operating element additionally for the winter, a heating wire can be worked into the spaced knit which, directed against the cover, ensures a rapid heat-up rate while the electric energy consumption is low.